1. Field of the Invention
The present invention relates to a display device having an improved structure and driving scheme that simplifies manufacturing processes and reduces cost.
2. Description of Related Art
An active type display device such as an active matrix (AM) liquid crystal display (LCD) and an active matrix organic light emitting display (OLED) includes a plurality of pixels arranged in a matrix and including switching elements and a plurality of signal lines such as gate lines and data lines for transmitting signals to the switching elements. The switching elements of the pixels selectively transmit data signals from the data lines to the pixels in response to gate signals received from the gate lines for displaying images. The pixels of the LCD adjust transmittance of incident light depending on the data signals. The pixels of the OLED adjust luminance of light emission depending on the data signals.
The display device further includes a gate driver for generating and applying the gate signals to the gate lines and a data driver for applying the data signals to the data lines. Each of the gate driver and the data driver generally includes a plurality driving integrated circuit (IC) chips. The number of the IC chips is preferably few to reduce manufacturing cost. In particular, the number of the data driving IC chips is important since the data driving IC chips are much more expensive than the gate driving IC chips.
An LCD includes a pair of panels provided with field generating electrodes and a liquid crystal (LC) layer having dielectric anisotropy, which is disposed between the two panels. The field generating electrodes generally include a plurality of pixel electrodes connected to switching elements such as thin film transistors (TFTs) to be supplied with data voltages and a common electrode covering an entire surface of a panel and supplied with a common voltage. A pair of field generating electrodes that generate the electric field in cooperation with each other and a liquid crystal disposed therebetween form a liquid crystal capacitor.
The LCD applies the voltages to the field generating electrodes to generate an electric field to the liquid crystal layer. The strength of the electric field may be controlled by adjusting the voltage across the liquid crystal capacitor. Since the electric field determines the orientations of liquid crystal molecules and the molecular orientations determine the transmittance of light passing through the liquid crystal layer, the light transmittance is adjusted by controlling the applied voltages, thereby obtaining desired images on the display.
To prevent image deterioration due to long-time application of the unidirectional electric field, etc., polarity of the data voltages with respect to the common voltage is reversed every frame, every row, or every dot.
Among the various inversion types, a dot inversion reversing the data voltage polarity every given number of pixels reduces vertical crosstalk or vertical flickering due to the kickback voltage, thereby improving the image quality. However, the polarity inversion of the data voltages flowing in each data line often requires complicated driving scheme that may cause signal delay. Although the signal delay may be reduced by using a low resistivity metal, it may complicate the manufacturing process and increase the production cost.
On the contrary, a column inversion reverses the voltage polarity every given number of pixel columns. Since the column inversion does not reverse the polarity of the data voltages applied to each data line during one frame, the problems associated with signal delay are remarkably reduced.
However, the column inversion technique is inferior to the dot inversion technique in terms of vertical crosstalk and vertical flickering, etc.